I doubt whether it comes down to tyre pressure – but interestingly, BMW recommends the same tyre pressure for the K1200RS – whether riding 1 up; 2 up; or 2up plus luggage ….. ie Front 2.5 (36psi) and Rear 2.9 ( 42 psi) ….so that begs more questions for those that are used to adjusting tyre pressures to suit loads ???